1. Technical Field
The present invention relates to redundancy for virtual private local area network (LAN) service (VPLS) in a communications network.
2. Background
Networks of general purpose computer systems and specialized devices connected by external communication links are well known and widely used in commerce. The networks often include one or more network devices that facilitate the passage of information between the computer systems. A network node is a network device or computer or specialized device connected by the communication links. An end node is a node that is configured to originate or terminate communications over the network. An intermediate network node facilitates the passage of data between end nodes.
A local area network (LAN) comprises multiple end nodes that share a communication link without an intervening intermediate network node. Such a communication link is called a network segment. A virtual LAN (VLAN) includes one or more intermediate network nodes called switches that forward data packets from one segment to another segment based on an identifier called a tag that indicates segments on the same VLAN.
A virtual private LAN service (VPLS) is offered by a wide area network (WAN) service provider (SP). In a VPLS, multiple LANs at remote sites for one customer are connected across a WAN, including the public Internet, as if on the same VLAN, without exposing the data packets to end nodes of different customers. To provide resilience against node failure, the SP point of presence (POP) on the WAN typically includes a pair of intermediate network nodes called network-facing provider edge nodes (NPEs).